Going in to the first Sundance showing of The Skeleton Twins, in which Kristen Wiig and Bill Hader play a troubled sister and brother coping with the legacy of their screwed-up family, I knew nothing about the film except that it was being billed as the movie that reunited the two former SNL teammates but wasn’t a comedy. Glancing at that photo above, I thought to myself: Hmmmmm, I hope it’s not one of those glum dysfunctional-family indie specials in which gifted comedians blank themselves out for the sake of art. I needn’t have worried. The Skeletons Twins is very much a drama, but it has lots of laughs, too — the kind of good, soul-ticking laughs that emerge, organically, from dramatic situations. Its tone is comparable to that of The Kids Are All Right or Alexander Payne’s films. The Golden Globes would have no problem nominating The Skeleton Twins in the Best Comedy or Musical category. Yet as directed and co-written by Craig Johnson, this is a tenderly sincere, and smart, and beguiling, and penetrating movie about the way that ordinary messed-up people can wind up stumbling through their lives. And let me say right up front: The two actors are fantastic together, every bit as powerful as Laura Linney and Mark Ruffalo were as the woundedly bound siblings of You Can Count on Me. But then, we already know from Bridesmaids what a knockout of a leading lady Kristen Wiig can be. It’s Bill Hader who’s the revelation. I think he could become a major screen actor.

Hader plays Milo, who is gay, depressed, and living in Los Angeles, where he has watched his long-ago dream of becoming an actor slide into the toilet. He’s got nothing to replace it: no purpose, no dream. That’s why, in the opening scene, he slips into the bathtub and lets the blood from his wrists flow. His failed suicide attempt lands him in the hospital and brings Maggie (Wiig), the twin sister he hasn’t seen or spoken to in 10 years, to his bedside. Clearly, something major split them up, but their chatty rapport hasn’t gone away, and Maggie, now in the position of helping to save her brother’s life, offers to take him to the Hudson Valley, NY, home she shares with her sweetly civilized caveman of a husband, Lance (Luke Wilson).

Hader, though he gives a totally serious performance, doesn’t dial back the bitchery, the haughty flip effeminicy and shade-throwing nightclub mannerisms. (The filmmaker has acknowledged that one of the things that proved to him that Hader could play the part was Hader’s popular SNL character Stefon, the insane-in-the-brain downtown party queen.) Yet what’s startlingly subtle about Hader’s performance is that even as he tosses off the drop-dead wisecracks and flashes an I-love-a-parade smile, it’s never the actor himself who’s “on.” It’s Milo, whose bitchery is built around a core of despair, and even dread, that Hader shows us between the lines. We don’t have to spend the whole movie waiting for the moment when it’s revealed that Milo, beneath the show he puts on, has feelings, damn it. Those feelings are there, alive, at every moment. And that, apart from how funny he is, is what’s really magnetic about Hader’s acting: Unlike, say, Will Forte, who was just fine, in his acerbically folded-in way, in Nebraska but didn’t necessarily make you want to run out and see more Will Forte movies, Hader, in The Skeleton Twins, has that magic, that indefinable something that connects him right up to an audience’s emotions. He’s a lightning rod of an actor.

At first, it seems like Milo, the cute lost child who has spent his life getting by on his adorableness and therefore never grew up, is the one in need of rescuing, and that Maggie, in her cozy home, with the doting husband she’s now officially trying to have a baby with, is the sane, warm, centered adult. But her issues come out in a quieter way. She has secretly put herself on birth control pills, and by the time she lets herself be seduced by her scuba-diving teacher, we know something is wrong, yet there’s a deep mystery to what that is: Does she want out of her marriage? Or is she too frightened to go forward with it? (Lance, played by Wilson as a likable lunk who’s a bit of a simpleton, could be her rock-solid ballast, or maybe he’s driving her nuts.) As Maggie and Milo reconnect, they begin, slowly, to wind back to the intimacy they had when they were younger, and they peel away each other’s defenses like onion skins. Wiig and Hader bring off something rare: They show you the spiritual romance that can be there even in a fraught brother-sister relationship. Wiig gives a very different kind of performance from her triumphantly frazzled acting in Bridesmaids. In The Skeleton Twins, she’s together on the surface, with little fragments of stress underneath, and an anger she doesn’t know what to do with. Yet here, once again, as in Bridesmaids, Wiig has a way of drawing the audience into a conspiratorial relationship with her character’s bad behavior. She’s acting out for all of us.

This is only Johnson’s second feature, but his voice as a filmmaker is sparkling, clear-eyed, and charged with feeling. When we finally learn what broke up Maggie and Milo 10 years before, the situation feels thorny and complicated in a deeply lifelike way. We can see how there was no resolving it, how issues of rivalry and love got all gummed up with each other. It’s clear that Johnson has the gift to make tenderly serious comedies about the way we are. At the same time, one of the things I like about his filmmaking is that he knows that a movie needs to let loose. There is, God forbid, a lip-syncing number right in the middle of The Skeleton Twins, but damned if it isn’t the most thrilling lip-syncing sequence since I can’t remember when. It features the 1987 Starship hit “Nothing’s Gonna Stop Us Now,” one of those song choices that make you think, at first, “How exquisitely cheesy!” and then, about halfway through, you’re thinking, “That’s the greatest song I’ve ever heard!” It’s all about the way that Bill Hader, as Milo, gives himself over to the music: He dresses up in it, miming its every jingle-jangle refrain like the anthem of optimism it must have been to Milo when he was growing up. And then, when Milo finally gets the reluctant Maggie to sync along with him, what you’re witnessing is the two of them bringing each other back to life. The Skeleton Twins isn’t flawless — I wish the film’s ending were a tad more resolved — but it’s a movie that I think a lot of people are going to want to see, because it lifts you up in an honest way.

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There’s been a lot of enthusiasm at Sundance for Laggies, the new romantic comedy from Lynn Shelton, the director of Your Sister’s Sister and Humpday. To me, the movie was perfectly okay, a reasonably enjoyable diversion, but I had the feeling that I always do at Shelton’s films: I kept wanting it to be better — to be more convincing, less cute, more real, less rambunctiously situational. Shelton has genuine talent, but she’s emerged as the poor woman’s Nicole Holofcener. Her films are never quite totally authentic in the way that Enough Said and Friends with Money were. Set in Shelton’s home town of Seattle, Laggies is centered around a woman who’s a hidden arrested development case. Keira Knightley, likable but a little too pert and poised for the role, plays Megan, who has been with the same emo geek for 10 years — they were chosen best couple at their high school prom — and doesn’t have the strength to admit to herself that she doesn’t want to be with him anymore. She’s in a funk, which she gets out of in a wacky way: She befriends a teenager, played by Chloë Grace Moretz (who has really bloomed as an actress), and starts hanging out with her. Then, when Megan is supposed to be away at a career retreat, she spends the week crashing at the home of her new teen buddy and the girl’s gruff Teddy bear of a single father (Sam Rockwell), who, of course, turns out to be the man she’s been looking for. It’s all shaggy and amusing, but also kind of diagrammed. I got a little restless, because Shelton — and this may be the problem — is pulling so many gears and levers to get you to like the people on screen that I just wished she’d let those levers go and see who those people might be without them.